This invention relates to a hearing aid, and more particularly to an ear insertion type hearing aid capable of being easily inserted into and removed from an ear hole.
Conventionally, as the main body of an ear insertion type hearing aid, in particular, a custom type hearing aid is in more intimate contact with an ear hole in addition to that the main body is made compact, a time-consuming job is increasingly required to insert and remove the hearing aid.
As a method of solving this problem, there has been conventionally proposed a hearing aid, as shown in FIG. 1, in which the case 2 of a hearing aide 1 is formed to adapt to the configuration of the external auditory miatus of a wearer and a U-shaped taking-out knob 5 is mounted on the surface of a panel 3 provided at the outside end of the case 2 together with components such as a gain regulator 4 with a power supply switch and the like.
The opposite ends of the taking-out knob 5 is turningly supported by a mounting hole 6 defined to the case 3 and the hearing aid 1 is inserted into an ear hole in the panel 3. At this time, the wearer previously turns OFF the power supply switch of the gain regulator 4 and inserts the case 3 into the ear hole by picking the case with his fingers, and then turns ON the gain regulator 4 and continues to adjust the same until the wearer can get a suitable volume of aid sound through an earphone (not shown) provided at the extreme end of the case 3.
On the other hand, when the hearing aid 1 is removed the ear hole, the power supply switch is returned to an OFF state and then the hearing aid 1 removed from the ear hole in such a manner that the taking-out knob 5 is lifted up and pulled by being picked with fingers.
Nevertheless, in the hearing aid 1 arranged as described above, since the gain regulator 4 with the switch is disposed on the panel independently of the taking-out knob 2, each time the wearer inserts or removes the hearing aid 1, he or she must turn ON or OFF the power supply to the gain regulator 4 with the switch to prevent the unnecessary consumption of a battery and in addition to that he or she must lift up or bring down the taking-out knob 4, and each time the wearer wears the hearing aid, he or she must controls a sound volume and these operations must be carried out in the narrow space around the ear hole by skillfully moving finger tips.
Conventionally, an ear insertion type hearing aid is devised so that it can be used inconspicuously in such a manner that a case containing a hearing aid signal processing circuit is inserted into the ear hole of a wearer and sound collected through a microphone mounted on a panel exposed to the periphery of the inlet of the ear hole is subjected to a hearing aid processing, as necessary, and then supplied to the interior of the ear hole as hearing aid sound through an earphone attached to the extreme end of the case.
This kind of the ear insertion type hearing aid may produce so-called howling in such a process that when the hearing aid is worn, hearing aid sound supplied to the interior of the external auditory miatus of a wearer from the earphone leaks out to the outside of the external auditory miatus through the gap between the case and the external auditory miatus wall of the wearer and returns again to the microphone.
This howling not only interrupts the function of the hearing aid but also makes the wearer very uncomfortable by the oscillating sound of high acoustic pressure.
As a method of preventing the occurrence of the gap, there is contemplated a method of making the outside diameter of the case at the portion thereof confronting the external auditory miatus of the wearer a little larger than the inside diameter of external auditory miatus of the wearer, but this method is disadvantageous in that it gives the wearer uncomfortableness and pain.
Conventionally, to solve this problem, there is a proposal for inserting a howling prevention band 14 around a case 13, as shown in FIG. 2.
The howling prevention band 14 is made of an annular elastic material and has three thin collars 14A, 14B and 14C formed around the outside periphery thereof.
An annular groove 12 is formed around the case 13 for positioning the howling prevention band 14 and the hearing aid 11 is worn in the state that the howling prevention band 14 is engaged with the groove 12.
According to this method, the howling prevention band 14 can prevent hearing aid sound supplied from an ear-phone from leaking through the gap between the case 13 and the external auditory miatus wall of a wearer to thereby avoid howling.
Neverthless, the conventional method has a draw-back in that when the wearer removes the hearing aid 11 from the ear, the howling prevention band 14 is stretched by the friction between the howling prevention band 14 and an ear wall due to the elasticity thereof and removed from the groove 12 of the case 13 and remains in the ear hole.